Consistancy in zero

I've got a 25-06 that I've been using for close to 30 years that shoots 3/4" groups all day long, but any difference in temperature will put the group into a different zero. I've got a 270 and a 7mm Rem mag that are very consistant in this regard, as was an earlier 7 mag, and is my buddie's 270.

Have any of you come up with a logical reason for this? I have a Ruger #3 that has never shot well (unlike two #1's that I have)and I've decided that rebarreling it would be a worthwhile project as soon as I can make up my mind as to what caliber. Most of my deer hunting is out of a backpack so I don't want anything really heavy; a good honest 500 yard rifle will do fine. I'm leaning towards a 270 Weatherby, simply because I don't have one, and it will do what I want in terms of velocity, but I'm concerned about consistancy as mentioned above. Dan Lilja recommends the 270 Weatherby but he believes that one cartridge is not more consistant than any other, and that my experiences with the 270 and 7 Rem mag are simply co-incidence

Any comments on this? I've been reloading and putting together custom rifles since the 222-250 was a wildcat and I'm reasonably knowlegable for a stupid amatuer.

Everything I been seeing with the 6.5wsm lately, man I'd jump on one of them in a heartbeat if even considering what you are. It is absolutely amazing at the 30" barrel length, the Ruger still would be real short with a 30 or 32" bbl too and 3250-3300 fps with a 140 is real doable at under 65k psi, I can tell you that much. Something you might look into. [img]images/icons/smile.gif[/img]

S1 has a good bit of experience with this wildcat too.

The POI shift in cold weather is something I haven't noticed, but it could be the powder is temp sensitive? You didn't say which one you'd been using. The Hodgdon Extreme line of powders are probably the best, although the Reloader 22 and 25 I've been using alot of have been outstanding too.

I've been using H4831 in all three rifles mentioned. I wasn't aware of the "extreme" powders until recently, and I assume that they are recent changes in Hodgen's powders, so I'm definately using information taken over many years. Why the WSM's? I notice they all have short necks. One of the things I like about the 270 Weatherby is the long neck, and it follows that the short neck of the 7 Rem mag is something I DON'T like.

Obviously, I'm relating the changing zeros in different temps with pressure differential.

I go elk hunting in CO in the late season, which is in early November. I always stop at a place just off the paved road and check zeros. My 7 mag is always right on, and my improved 35 Whelen is always three or four inches off. When I get back home, it's right on again.

I'll try the Extreme powders; you guys might be on to something there. I hope. Thanks for your help.

There are some details missing about your quandry with the 25-06 but I assume you're talking about cold barrel group shift. I'd be looking at the bedding and or fore end warp pressing upon the pressure pad differently as the temps change. I'd guess that barrel stress could cause it but think that would show up more during a string instead of between different groups.

JMBN, is the stock on your 270 Wood? My guess is that the stock is warping and moving your POI. Free float the barrel and this problem will go away. Good bedding helps too.

As to the Extreme powder, I am a big supporter for hunting. Living in Canada, I see big swings in temp during a day. Conventional powders will vary up to 3fps per deg of F change. That means a load can easily vary by 100fps in my climate. This affects POI, accuracy, drop. By using Extreme powders, I have found my POI to not shift from summer to winter. Vel. are consistent too. Great stuff.

My favorites are the H4350, H4831SC and Varget. Using CCI BR2 primers, I get 1/3 MOA or better from "hunting" rifles.

As to sugg. for a new cartridge, I too would lean towards the 270WSM in this calibre. Great performance and longer effective barrel length. Throat wear should be lower then the WBY too.

If choosing any cartridge, then I would look at the 6.5 cal and 7mm, simply because there are so many great bullets to choose from.

I have had excellent success with the Hornady SST for accuracy and BC. Tougher then the Nosler BT too.